Why did Mendeleev leave blank spaces between zinc (Zn) and arsenic (As)?

1 Answer
Feb 15, 2016

Answer:

Because at the time he published the table, neither gallium nor germanium had been characterized.

Explanation:

Mendeleef published the first version of the Periodic Table in 1869; at that time, neither gallium nor germanium had been characterized.

So in the original publication of the Table, Mendeleef was shrewd enough to realize that not ALL of the elements had been identified. The discoveries of gallium and germanium AFTER the Table had predicted their likely existence was evidence of the utility of Mendeleef's periodic approach.